The acetylcholine receptor in the electric tissue of Electrophorus electricus is to be chemically and physically characterized both in membrane fragments and in detergent-solubilized and purified state. The subunit structure of the receptor is to be determined by affinity labeling, sodium dodecyl sulfate-gel electrophoresis, determination of amino acid composition and terminal sequences. The reconstitution of purified receptor and other membrane components into membrane responsive to cholinergic agents will be attempted.